In the field of electrochemical sensors, there is a biosensor which uses enzymes for measuring the glucose concentration (glucose level) in the blood. For example, there is a biosensor configured by comprising a base plate in which a working electrode and a counter electrode are formed on an upper surface, a spacer which is superimposed on the base plate so as to form a groove facing a part of the working electrode and the counter electrode, respectively, a reactive site in which a reaction reagent layer is formed on a part or all of the groove, and a cover plate which is superimposed on the spacer, wherein a space that is surrounded by the groove and the cover plate forms the bodily fluid passage, and wherein a terminal part which is caused to conduct respective with the working electrode and the counter electrode and come in contact with a terminal of the body is disposed at an appropriate location on an upper surface of the base plate (for example, Patent document 1).
The biosensor described in Japanese Patent Application Laid-open No. 2006-314831 is integrally formed with a tool referred to as a lancet for opening a small hole (scratching) the skin; for instance, the fingertip, of a patient. A bodily fluid passage, in which the reactive site faces the inner surface thereof, is formed on the inside of the biosensor in the thickness direction thereof on the one hand, and a through-hole having a diameter that is larger than the puncture tool which is in communication with the bodily fluid passage and allows the passage of the tip of the puncture tool, and which penetrates the sensor in the thickness direction thereof and is opened to the lower surface of the sensor is also formed in the biosensor. Consequently, the blood that flows from the skin that was scratched by the puncture tool is introduced to the reactive site from the through-hole through the bodily fluid passage.    [Patent document 1] Japanese Patent Application Laid-open No. 2006-314831